He didn't necessarily need development. He was used a plot device, which I actually liked because it gave Hawkeye a purpose in the film. Not every character needs development, as long as they're there for a reason.

Even though you liked it Renner didn't. Even though it's just my speculation actors have left roles for just that before.

All I'm saying is that we've heard of every single character having something to do in Phase 2 except Hawkeye. I may be over thinking it but that kinda has me worried